1. Field of the Invention
The present invention relates to an image capturing apparatus, an image capturing method, and a computer-readable medium storing program. More particularly, the present invention relates to an image capturing apparatus which obtains images having high dynamic range.
2. Description of Related Art
Image capturing apparatuses, such as digital cameras and video cameras, obtain an image by converting an optical image of a subject into an electrical signal by image sensing devices, such as CCD and MOS. However, the dynamic range of these image sensing devices is remarkably lower than dynamic range that exists in real life. Consequently, a conventional image capturing apparatus adjusts optical information of a main subject within the dynamic range of the image sensing devices to obtain an image using an optical stop, an electronic shutter and the like. For this reason, when a subject includes an area having high dynamic range, there has been a problem that the conventional image capturing apparatus can obtain only images that ranges from a predetermined brightness to a predetermined darkness.
A Japanese patent application publication No. 11-32242 discloses an image capturing apparatus which generates images with high dynamic range by compounding signals acquired by a plurality of CCDs having different sensitivity. Also, a Japanese patent application publication No. 5-260391 discloses an image capturing apparatus, where the image capturing apparatus is adapted to increase the amount of charges by reading charge pattern accumulated in CCD for multiple times so that the dynamic range of the image is expanded.
However, since the image capturing apparatus disclosed in the Japanese patent application publication No. 11-32242 requires optics, such as a plurality of CCDs and a beam splitter, large-size and high-cost of the apparatus cannot be avoided. Moreover, in the image capturing apparatus disclosed in the Japanese patent application publication No. 5-260391, although the amount of charge transfer from the CCD can be increased, the dynamic range cannot be expanded unless increase of the amount of charge storages is accomplished.